Specific binding of 125I-labelled glucagon-like peptide-1(7–36)amide (GLP-1(7–36)amide) to rat insulinoma-derived RINm5F cells was dependent upon time and temperature and was proportional to cell concentration. Binding of radioactivity was inhibited in a concentration-dependent manner by GLP-1(7–36) amide consistent with the presence of a single class of binding site with a dissociation constant (Kd) of 204± 8 pmol/l (mean ± s.e.m.). Binding of the peptide resulted in a dose-dependent increase in cyclic AMP concentrations (half maximal response at 250 ± 20 pmol/l). GLP-1(1–36)amide was approximately 200 times less potent than GLP-1(7–36)amide in inhibiting the binding of 125I-labelled GLP-1(7–36)amide to the cells (Kd of 45±6 nmol/l). Binding sites for GLP-1 (7–36)amide were not present on dispersed enterocytes from porcine small intestine. J. Endocr. (1988) 116, 357–362